It is well known to reinforce the structural members of a vehicle body by welding or otherwise suitably attaching a metal panel to overlie the structural member or to overlie portions of adjoining structural members at a body joint.
It is also known to reinforce a vehicle structural member by filling a cavity in the structural member with a structural foamed plastic. A disadvantage of filling a cavity with foamed plastic is that the flow of air is prevented so that moisture can be entrapped inside the structural member. The aforedescribed reinforcing techniques are used in whichever portions of the vehicle structure might require stiffening, reinforcing, strengthening or stabilizing. One such example of the use of a foamed plastic is shown in Kramer U.S. Pat. No. 3,909,058 issued Sept. 30, 1975.
It is also known to reinforce plastic structures formed of SMC and BMC materials by the addition of hollow glass microspheres, also known as glass bubbles and micro balloons. These microspheres may be made of a plastic such as phenolic or polyvinyladene chloride or from an inorganic material such as glass and have a diameter of 0.020 mm. to 0.150 mm. This use of microspheres is known to reduce weight, improve impact resistance, and add stiffness. As such these microspheres filled syntactic foams have found use in the boating, aircraft, automotive and furniture industries. Furthermore, such microspheres may be mixed with a curable thermosetting resin to make a granular mixture which may be packed into a shaped cavity as taught by Murphy U.S. Pat. No. 4,405,543 issued September 1983.
It is also known to form a macrosphere by use of a resin to bond together a large number of microspheres into a larger sphere having a diameter of 0.5 to 10 millimeters. These macrospheres can also be used in a foam and are useful in boat hull construction and other floatation structures requiring high strength and light weight. Miessler et al U.S. Pat. No. 4,040,165 issued August 1977 is an example of such a buoyant structure in which a syntactic foam fills the voids between glass macrospheres.
The present invention provides a new and improved reinforcement method and apparatus whereby glass macrospheres may be employed to reinforce a structural member without preventing airflow therethrough.